Method and system for automatically attaching sub-assembly to main assembly using industrial robots

A system for automatically attaching a sub-assembly to a main assembly, the main assembly being transported on a conveyor belt and having a positioning portion at a predetermined position thereof on a basis of which the sub-assembly is fixedly attached to the main assembly by means of fastening means and a predetermined number of holes around the positioning portion and the sub-assembly by means for securing the sub-assembly to the main assembly by means of said fastening means and an engagement portion at a predetermined position thereof, comprising:

• (a) an automatic fastening tool which operatively fastens said fastening means to said securing means of the sub-assembly via the corresponding holes of the main assembly so that the sub-assembly is fixedly attached to the main assembly at the predetermined position of the main assembly;
• (b) a supporting arrangement which supports said fastening tool, said supporting arrangement including a base member fixed to a multi-articulated arm of at least one robot, a movable member supported on said base member in parallel thereto so as to be operatively floatable with respect to said base member and on which said fastening tool is fixedly supported, first means, interposed between said movable member and base member, for locking and unlocking said movable member so as to render said movable member respectively fixed and floatable with respect to said base member, an engagement member attached to said movable member for engaging the engagement portion of the sub-assembly, said first locking means locking said movable member when said engagement member is engaged with the engagement portion of the sub-assembly, and a guide member attached to said movable member for engaging with said positioning portion of the main assembly in such a way that said member is moved toward a center of positioning portion of the main assembly, said locking means unlocking said movable member so as to passively float in accordance with the movement of said guide member when said guide member is engaged with the positioning portion of the main assembly;
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• (c) a hand arrangement, including a main frame fixed to another multi-articulated arm of said robot, a pair of clamping members which operatively grasps the sub-assembly in such a way that the sub-assembly is fixedly grasped when said engagement member of said supporting arrangement is engaged with the engagement portion of the sub-assembly so as to position said fastening tool relative to the sub-assembly and the sub-assembly is floatingly grasped at least along a plane parallel to that of the positioning portion of the main assembly when said guide member of said supporting arrangement is engaged with their positioning portion of the main assembly so as to position said fastening tool and sub-assembly with respect to the main assembly, and second means for locking and unlocking said pair of clamping members so as to render the sub-assemby fixedly grasped and floatingly grasped by said pair of clamping members.